1. Technical Field:
This invention relates to lances such as used for introducing an inert gas into molten metal for stirring the same or for injecting a stream of oxygen into molten metal for refining the same.
2. Description of the Prior Art:
Lances for introducing gases into molten metal for various purposes are disclosed in U.S. Pats. Nos. 3,379,428 and 3,082,997 wherein the lances incorporate straight metal tubes forming a plurality of gas conduits arranged to direct gas downwardly into the molten metal in which the lance is positioned.
U.S. Pat. Nos. 3,645,520 and 3,898,078 disclose lances in which the gas conveying conduits are formed in several patterns.
None of the prior art known to applicant has disclosed a structure in which argon gas or the like is introduced into the lance and directed through the body thereof in a manner to shield the outer surfaces of the lance and particularly the upper portions thereof which are in direct contact with molten slag on the molten metal whereby the areas thereof normally subjected to rapid erosion are shielded by an annular current of rolling, swirling molten metal around the lance which serves to move the lighter molten slag away from the lance.
The present invention relates to a substantially improved lance for treating molten metals in which the principal body of the lance is formed of a refractory material with a bore extending longitudinally through a portion of the refractory material and terminating inwardly of the delivery end of the lance where it communicates with a plurality of metal tubes each of which may be shaped to form a controlled limited passageway of a desired size with the distal ends of the metal tubes communicating with the delivery end of the lance and of equal importance wherein some of the plurality of metal tubes forming passageways communicate with the bore extending longitudinally therein in areas of the lance inwardly of the first or upper end thereof and with the exterior of the lance whereby the distal ends of these metal tubes direct gas flowing therethrough into an annular column around the exterior of the lance creating an annular rising column of molten metal which serves to protect and shield the upper portions of the lance from the slag on the molten metal. In addition to or in place of the tubes communicating with the exterior of the lance, the refractory body may be porous refractory with interconnecting cavities so that gas delivered into the interior of the body will flow through the porous refractory and be delivered over the surface of the refractory body where it will form bubbles flowing upwardly and thereby create annular rising columns of swirling, mixing molten metal which will move molten slag thereon away from the lance and thus shield the same from the erosion which would otherwise result.